1. Field of the Invention
The present invention is related to a reticle storing container, and more particularly, to a reticle storing container used in the EUV lithography process.
2. Description of the Prior Art
In the rapidly developing modern semiconductor technology, optical lithography tool plays an important role. The pattern definition relies fully on optical lithography technology. In the application of optical lithography tool related to semiconductors, pre-designed circuit paths are fabricated as light-transparent reticle in specific form. Basing on the principle of exposure, after light from the light source passes through the reticle and is projected on a silicon wafer, specific circuit pattern can be exposed on the silicon wafer. However, since any kind of dust (such as particles, powders, and organic matters) adhering to the reticle can cause degradation of the quality of the projected pattern, the reticle used to produce pattern on silicon wafers is required to be kept absolutely clean. Therefore in ordinary wafer processes, clean rooms are provided for preventing from contamination caused by particles in the air. However, the status of absolute dustless is still inaccessible in clean rooms at present. In current semiconductor processes, anti-contamination reticle pods are used for storing and transporting reticles to ensure the cleanliness of reticles.
In recent years, in order to further scale down the chip feature sizes, EUV (extreme ultraviolet light) at a wavelength of 157 nm is applied in lithography tool for the pattern on reticle to be imaged with higher resolution when being projected on the surface of a silicon wafer. However, when EUV is applied, the requirements for cleanliness of reticle pod are also, relatively speaking, higher. Particles smaller than 30 micrometers are previously acceptable, but as far as reticle pods for use with EUV lithography techniques are concerned, only particles with sizes between 30 and 50 micrometers are acceptable.
Then, referring to FIG. 1, which is a container for reticle transportation used in EUV lithography process of the prior art. At least one reticle pod 81 is disposed in the container for reticle transportation 80, and the reticle pod 81 is purged with clean gas and accommodates a reticle R. Moreover, the container for reticle transportation 80 includes a thermophoretic source 82, dry ice for example. The temperature of the side 81A of the reticle pod 81 that is close to the thermophoretic source 82 is lower, and therefore particles in the reticle pod 81 can be driven to move toward or gather on the side 81A that is close to the thermophoretic source and will not adhere to the surface of the reticle R. With the aforementioned container for reticle transportation 80, it seems that the particles can be controlled. However, if the thermophoretic source 82 is used to drive particles away from the reticle R, then the particles that are originally located above the reticle R may then adhere onto the reticle R. Therefore, a container for reticle transportation to be used in EUV lithography process is still urgently needed.